"Immoral." "Heartbreaking." Civic leaders from around the world Thursday condemned President Donald Trump’s decision to renege on the U.S. commitment to the Paris climate accord but said they’ve been preparing for this outcome for months and it won’t set back their commitments to cut carbon emissions.

In a statement released by the C40 Cities Climate Leadership Group, chairwoman Anne Hidalgo — the first mayor of Paris — urged the U.S. administration to reconsider its "dramatic mistake" but suggested that much can be accomplished by cities despite this leadership void.

"Regardless of President Trump’s decision, the greatest cities of the world, in particular the 12 American C40 cities, remain resolutely committed to doing what needs to be done to implement the Paris Agreement," Hidalgo said in a statement. "Not a single day goes by without C40 mayors on every continent making bold and pioneering choices, serving citizens of the future. We will be relentless. The evidence and urgency of the climate crisis, as well as the economic potential in shifting towards a greener future, leaves us with no alternative."   

Her sentiment was echoed by Clover Moore, lord mayor of Sydney: "What’s heartbreaking is the damage governments can do in a short time when they’re in power. But where national action falters, as we see in the USA tonight, we see more and more city governments stepping up to provide the leadership we urgently need."

Ninety-one major cities are in the C40 network, representing more than 650 million people. Partnering with consulting firm Arup, the group released a report Thursday recommending that cities focus on reaching "peak emissions" by 2020 and then acting to halve them on a per-citizen basis over the next decade, cutting them from an average of 5 tons carbon emissions per capita to 3 tons CO2e per capita by 2030. Actions within the next four years will be particularly important if the world is to achieve its goal of limiting global temperature increase of below 1.5 degrees Celsius.

Not a single day goes by without C40 mayors on every continent making bold and pioneering choices, serving citizens of the future. We will be relentless.

The report, Deadline 2020: How Cities Will Get the Job Done, suggests that U.S. cities — which already have collectively embraced more than 2,400 individual actions meant to fight carbon emissions — will play a pivotal role in the success or failure of this effort. If all U.S. cities were to follow the lead of the C40 players in the United States, they could contribute more than one-third of the emissions reductions needed to help meet the U.S. commitments to the Paris accord. The U.S. C40 cities are Seattle; Portland, Ore.; San Francisco; Los Angeles; Chicago; Houston; New Orleans; Boston; New York; Philadelphia; Washington and Austin, Texas. 

In the aftermath of the Trump press conference to dump Paris, Washington Mayor Muriel Bowser said she has a "special obligation" to continue support for programs that will develop a low-carbon economy in the nation’s capital, which include one of the biggest municipal solar projects in the country and the largest wind power purchase agreement. 

"Going forward, our commitment to wind and solar will not yield, and we will move forward with building a more sustainable D.C.," Bowser said in a statement. "At a time when our country should be leading the fight against climate change, it is disappointing to see us retreating into isolation. Fortunately, I am confident that leaders around the country will continue to think globally, act locally and ensure that the U.S. remains a strong partner in the fight against climate change."

Mitchell Landrieu, mayor of New Orleans, linked climate change to the fastest coastal losses in the United States and described it as one of his city’s most urgent threats. "Although the Trump administration questions the facts of climate change, we must not waver," he said. "As mayors on the front lines of leadership, we need to keep our commitment to our communities and to each other, working together to transition to a low-carbon economy that not only helps manage our climate risk, but also creates new businesses, jobs and wealth."

The reaction from New York Mayor Bill De Blasio was swift and biting, and he likewise reiterated an intention to honor the Paris commitment. "President Trump can turn his back on the world, but the world cannot ignore the very real threat of climate change. This decision is an immoral assault on the public health, safety and security of everyone on this planet."